Quantum Tunneling of Magnetization

Abstract

In the past couple of years, interest in Quantum Tunneling of Magnetization (QTM) has grown significantly. Since the phenomenon had tended to be regarded as a mere curiosity and mathematical game for theorists to play around with, QTM had to wait for the recent experimental work being carried out at Grenoble, Barcelona, and IBM-Yorktown in order to be of great interest to experimentalists at large. Most of the basic theoretical groundwork has been laid; we present an introduction to the theory and a summary of the results thereof. We look forward to experimentalists to refine techniques of preparing and characterizing samples, making magnetic measurements, and, with the help of theoretical analysis, improving on our ability to analyze and interpret data from magnetization measurements. We can be sure that QTM is manifested in experimental results only when we have carried out a thorough analysis of the full range of manifestations of classical processes. In this regard, we discuss the work of Bernard Barbara and this author in developing further the theory of magnetic relaxation in composites by introducing the barrier plot, which is a surface plot of the distribution of energy barriers with respect to both the energy and the applied field. Next, we discuss the domain wall junction, which has great potential in exhibiting QTM. Finally, we discuss the role of dissipation in QTM.